1. Field of the Invention
The present invention relates to a liquid crystal display (xe2x80x9cLCDxe2x80x9d) apparatus and a method of manufacturing thereof, and more specifically, to a method of manufacturing and structure of an LCD apparatus which eliminates stitching defects caused by an irregularity in a width of a gate line or data line.
2. Description of the Background Art
In general, a liquid crystal display device includes a TFT array substrate. In the structure of the TFT array substrate as shown in FIGS. 1 and 2, a plurality of gate bus lines 60 are arranged horizontally and are spaced from each other by a certain distance. A plurality of data bus lines 70 are arranged vertically and are spaced from each other by a certain distance. The gate bus lines 60 and the data bus lines 70 are arranged so that the data bus lines 70 and the gate bus lines 60 intersect each other so as to define a matrix array.
A gate pad 60a and a data pad 70a which are in contact with a drive IC are defined at the end of the gate bus line 60 and the data bus line 70. A pixel electrode 40 is defined in each block area defined by the intersections of the gate bus line 60 and the data bus line 70 and a TFT 50 is also defined at the intersection point of the gate bus line 60 and the data bus line 70.
The TFT 50 includes a gate electrode 60b which is made from material used to form the gate bus line 60, a source electrode 70b and a drain electrode 70c which are made from a material used to form the data bus line 70, and a semiconductor layer 90. The drain electrode 70c of the TFT is in contact with the pixel electrode 40.
A display device that is manufactured by simultaneously defining a gate bus line and a data bus line is suitable when forming a large LCD with the above-mentioned structure, which has more than a 14 or 15 inch display area. However, due to technical limitations in manufacturing such a display device, the size of an area that can be exposed at one time is limited. For example, for large panels, a one-shot exposing process cannot be used since the panel is too large for conventional exposing equipment.
Therefore, in order to expose a large substrate, a divided exposure method is used. In the divided exposure method, a first portion of a substrate is exposed first and then a second, remaining part of the substrate is exposed. However, using the divided exposure method results in a difference in line width at a boundary line between the first area exposed by the first exposing step and the second area exposed by the second exposure step. Note that this difference in line width causes a difference in the resistance in the lines, which causes differences in luminance in the display. This luminance difference is called a stitching defect.
As shown in FIG. 3a, a metal layer 55 in which a desired pattern is to be defined is disposed on a transparent substrate 10 using the divided exposure method. In order to perform the divided exposure method on a large substrate 11 which is covered with a photo resist layer 80, the area of the photo resist layer is divided into part A and part B. An exposure mask 100, which exposes part A of the photo resist layer 80 and a border line D that divides parts A and B are located in the same position. The exposure mask 100 includes an exposure pattern 150 which is used to patter part A of the photo resist layer [of part A] of the substrate 11 into a certain pattern and a light blocking member 140. A light such as a UV ray which radiates from an exposure device on the exposure mask 100 penetrates the exposure pattern 150 and exposes the photo resist of part A of the substrate 11 with a certain pattern.
Then, an exposure mask 200 is located to be aligned with the border line D in order to expose part B of the photo resist layer 80 after eliminating the prior exposure mask 100 as shown in FIG. 3b. The exposure mask 200 includes an exposure pattern 151 and a light blocking member 141 in order to exposure part B of the photo resist layer 80 of the substrate 11. A light such as a UV ray which radiates from an exposure device on the exposure mask 200 penetrates the exposure pattern 151 and exposes the photo resist of part B of the substrate 11 with a certain pattern so at the end parts A and B which are divided by the border line D of the exposure mask are exposed into a certain pattern.
After exposing the photo resist into a certain pattern using each exposure mask 100 and 200, the photo resist layer 80 is developed and while using the developed photo resist pattern layer as a mask, a lower metal layer 55 is etched to define a data bus line 70 and a drain electrode 70c having a structure as shown in FIG. 4. A width (a) of a line such as the data bus line 70, which is located at the border part D of the divided exposure, is formed differently from widths (b) and (c) of the data bus lines 70 that are directly adjacent to the dividing line D as shown in FIGS. 4 and 5. The reason for the difference in the width pattern of the line formed at the border part of the divided exposure is because a metal layer is etched along the pattern of the photo resist. In other words, when resetting and attempting to locate the exposure mask 200 at an identical position after partly exposing the photo resist with the exposure mask 100, the rest of the photo resist is exposed in a state in which the location of the pattern of the exposure mask is slightly out of place or misaligned due to an error in positioning of the mask and the metal layer is etched according to such a pattern of the photo resist.
The patterned width (a) of the data bus line 70 at the border part D of the divided exposure is wider than the widths (b) and (c) of the data bus lines 70 which are directly adjacent to the dividing line D if the exposure mask 200 is placed to the right of line D as shown in FIG. 4. On the other hand, the patterned width (a) of the data bus line 70 at the border part D of the divided exposure is narrower than the widths (b) and (c) of the data bus lines 70 that are directly adjacent to the dividing line D if the exposure mask 200 is placed to the left of line D as shown in FIG. 5.
The substrate 11 of an LCD apparatus includes the pixel electrode 40 in contact with the drain electrode 70c. The TFT is formed such that the data bus line 70 is formed in the above described manner. When the screen of an LCD apparatus including each one of the pixel electrodes 40 is checked by applying power to the data pad 70a at an end of the data bus line 70 and the gate pad 60a at an end of the gate bus line 60, the problem of the stitching defect is determined at the border part D of the divided exposure.
The stitching defect is identified by a difference in the resistance value of each line and this difference in resistance is due to the fact that the width (a) of the data bus line 70 at the border part D of the divided exposure is different from the widths (b) and (c) of the data bus lines 70 that are directly adjacent to the dividing line D. Therefore, when using the divided exposure method for making a large substrate, the occurrence of the stitching defect still cannot be avoided even though there is some improvement in the degree of occurrence compared to suing an exposure method which exposes a substrate using a one-shot exposure process.
Preferred embodiments of the present invention overcome the problems of the conventional art described above by correcting the stitching defect which occurs at the border area of the divided exposure when the gate bus line and the data bus line are patterned using conventional divided exposure methods.
In a preferred embodiment of the present invention, a liquid crystal display includes a substrate, a plurality of gate lines disposed on the substrate, a plurality of data lines disposed on the substrate and arranged to define a matrix pattern with the plurality of gate lines, a plurality of thin film transistors connected to the gate lines and data lines, and a plurality of pixel electrodes connected to the thin film transistors, wherein a stitching defect correction element is included in at least one of the plurality of data lines.
In another preferred embodiment of the present invention, a method of a manufacturing liquid crystal display device includes the steps of forming a TFT array substrate in which a stitching defect correcting element is formed in between at least one of a plurality of data bus line and a data pad, and forming a wave shaped pattern with a width narrower than that of the data bus line at a selected stitching defect correcting element.